Valve structure for hydraulic circuit

Abstract

A valve comprises a spool with a land received in a bore of a valve body. The land is formed with at least one transfer passage. The land and cylindrical inner wall of the bore cooperate with each other to prevent any passage other than the transfer passage from opening between an inlet port and an outlet port. The transfer passage is always open to the outlet port and selectively uncovered by the cylindrical inner wall to communicate with the inlet port in response to movement of the spool.

What is claimed is: 
     
       1. A hydraulic control circuit for an automatic transmission, comprising: an oil pump as a source of hydraulic fluid;   a system pressure line connected to said oil pump;   a pressure regulator valve consisting essentially of: a valve body formed with a bore having a longitudinal center line, said valve body being formed with an inlet port connected to said system pressure line and an outlet port,   said valve body including a cylindrical inner wall defining said bore and formed with an inflow groove communication with said inlet port and an outflow groove communication with said outlet port, said inflow and outflow grooves being recessed from said bore into the cylindrical inner wall and spaced from each other along said longitudinal center line to define therebetween a cylindrical inner wall segment,   said cylindrical inner wall segment having an edge adjacent said inflow groove; and   a spool within said bore for movement along said longitudinal center line, said spool including a land opposed to said cylindrical inner wall segment, said land being in sliding fit to said cylindrical inner wall segment during movement of said spool to close a clearance between said land and said cylindrical inner wall segment,   said land being formed with a plurality of transfer passages bounded within said land, each of said plurality of transfer passages being in the form of a groove that extends along said longitudinal center line,   said plurality of transfer passages being separated from each other, each of said plurality of transfer passages having one end wall and other end wall and extending from said one end wall to said other end wall, each of said plurality of transfer passages having a predetermined section extending from said one end wall to a point between said one end wall and said other end wall,   said predetermined section of each transfer passage being opposed to said cylindrical inner wall segment and prevented from communicating with said inflow groove when said spool assumes a predetermined position relative to said valve body,   said predetermined section of each transfer passage being brought into opposed relation to said inflow groove gradually as said spool moves from said predetermined position within a predetermined stroke of movement of said spool relative to said valve body,   said edge of said cylindrical inner wall segment and said predetermined section defining various flow cross sectional areas as said spool moves from said predetermined position within said predetermined stroke of movement of said spool relative to said valve body.     
     
     
       2. The hydraulic control circuit as claimed in claim 1, wherein effective flow cross sectional area of flow through said inlet port, said transfer passages and said outlet port is variable in response to movement of said spool. 
     
     
       3. The hydraulic control circuit as claimed in claim 2, wherein each of said transfer passages has one end and opposite end that are spaced a distance along said longitudinal center line, wherein each of said transfer passages has a width unaltered over the entirety of said distance, and   wherein each of said transfer passages has variable depths along said distance.   
     
     
       4. The hydraulic control circuit as claimed in claim 2, wherein said one end wall and said other end wall of each of said transfer passages are spaced a distance along said longitudinal center line,   wherein said predetermined section of each of said transfer passages has variable widths along said distance,   wherein each of said transfer passages has a depth unaltered over the entirety of said distance.   
     
     
       5. The hydraulic control circuit as claimed in claim 1, wherein said land of said spool includes two spaced land-like projections and a sleeve interconnecting said two spaced land-like projections to define a continuous space inward of said sleeve, and wherein said sleeve is formed with a window opening to said continuous space thereby defining said plurality of transfer passages.   
     
     
       6. A valve consisting essentially of: a valve body formed with a bore having a longitudinal center line, said valve body including a cylindrical inner wall and two end walls spaced along said longitudinal center line and interconnected by said cylindrical inner wall to define said bore,   said valve body being formed with an inflow groove that is recessed from said bore into said cylindrical inner wall,   said valve body being formed with an outflow groove that is recessed from said bore into said cylindrical inner wall,   said inflow and outflow grooves dividing said cylindrical inner wall into a plurality of wall segments including a predetermined wall segment that separates said inflow groove from said outflow groove, said predetermined wall segment including an edge adjacent said inflow groove; and   a spool within said bore for movement along said longitudinal center line, said spool including a land, said land being opposed to said predetermined wall segment and in sliding fit to said predetermined wall segment during movement of said spool to close a clearance between said land and said predetermined wall segment,   said land being formed with a plurality of transfer passages bounded within said land, each of said plurality of transfer passages being in the form of a groove that extends along said longitudinal center line,   said land being opposed to said predetermined wall segment and in sliding fit to said predetermined wall segment to close a clearance between said land and said predetermined wall segment during movement of said spool relative to said valve body over substantially all stroke allowed for said spool to move along said longitudinal center line,   each of said plurality of transfer passages being open to said outflow groove over substantially all stroke allowed for said spool to move along said longitudinal center line,   said plurality of transfer passages being separated from each other, each of said plurality of transfer passages having one end wall and other end wall and extending along said center line from said one end wall to said other end wall, each of said plurality of transfer passages having a predetermined section extending from said one end wall to a point between said one end wall and said other end wall,   said predetermined section of each transfer passage being opposed to said predetermined wall segment and prevented from communication with said inflow groove when said spool assumes a predetermined position relative to said valve body,   said predetermined section of each transfer passage being brought into opposed relation to said inflow groove gradually as said spool moves from said predetermined position within the stroke allowed for said spool to move along said center line relative to said valve body,   said edge of said predetermined wall segment and said predetermined section defining various flow cross sectional areas as said spool moves from said predetermined position within the stroke allowed for said spool to move along said center line relative to said valve body.   
     
     
       7. A valve as claimed in claim 6, wherein said one end wall of each of said plurality of transfer passages is spaced a distance from said other end wall along said longitudinal center line and leading to said other end wall with respect to movement of said spool in a direction from said outflow groove toward said inflow groove. 
     
     
       8. A valve as claimed in claim 7, wherein each of said plurality of transfer passages has a width unaltered over said distance from said one end to said other end; wherein said predetermined section of each of said plurality of transfer passages has a first slope adjacent said one end to provide variable depths over a first predetermined distance from said end toward said other end;   wherein said predetermined section of each of said plurality of transfer passages has a second slope connected with said first slope to provide variable depths over a second predetermined distance, beyond said first predetermined distance, from said one end toward said other end, said second predetermined distance being greater than said first predetermined distance;   wherein each of said plurality of transfer passages has a flat bottom connected with said second slope to provide a depth that is unaltered over a third predetermined distance, beyond said first and second predetermined distances, from said one end toward said other end; and   wherein said first and second slopes have different gradients.   
     
     
       9. A valve as claimed in claim 7, wherein each of said plurality of transfer passages has variable widths that gradually increase form said one end toward said opposite end; and wherein each of said plurality of transfer passages has a depth that is unaltered over the entire length from said one end to said opposite end.   
     
     
       10. A valve as claimed in claim 7, wherein each of said plurality of transfer passages has a width unaltered from said one end to said other end; and   wherein each of said plurality of transfer passages has a cylindrical bottom wall interconnecting said one and other ends to provide variable depths from said one end to said other end.   
     
     
       11. A valve as claimed in claim 7, wherein said land includes a first land section and a second land section, said first land section being kept in contact with said predetermined wall segment and formed with said plurality of transfer passages; and wherein said first and second land sections are spaced from each other to provide a path for a tool for cutting said plurality of transfer passages.   
     
     
       12. A valve as claimed in claim 11, wherein said second land section is kept in contact with the adjacent wall segment that is disposed on the remote side of said outflow groove from said inflow groove. 
     
     
       13. A valve as claimed in claim 7 wherein said land includes spaced first and second land-like projections and a sleeve interconnecting said first and second land-like projections; and wherein said sleeve is formed with a plurality of windows, each extending between said one and said other end to define one of said plurality of transfer passages.